Low-loss P-i-n diode

Abstract

A low-loss P-i-n diode includes an i-type layer consisting of first and second i-type regions formed on the cathode layer of the diode and the i-type has a thickness W i of less than 25 μm. The impurity concentration of the first i-type region is higher than that of the second i-type region. To obtain a good forward-voltage V f , W i 2 /τ is selected to be in the range of 20-200cm cm 2/sec and the carrier lifetime τ of the i-type layer is controlled by a carrier lifetime killer with a small resistivity compensation effect which is diffused into the i-type layer. The P-i-n diode has a high reverse breakdown voltage, small forward-voltage drop and a short recovery time.

What we claim is: 
     
       1. A P-i-n diode comprising: a semiconductor substrate of a first conductivity type which functions as the anode of the P-i-n diode;   a first i-type layer of said first conductivity type formed on said semiconductor substrate and having a first thickness W 1  ;   a second i-type layer of said first conductivity type formed on the first i-type layer and having a second thickness of W 2  ;   said second i-type layer having an impurity concentration lower than that of said first i-type layer;   carrier lifetime killer characterized by a small carrier compensation effect being diffused into said first and second i-type layers whereby said first and second i-type layers have a carrier lifetime of τ; and   a region of second conductivity type diffused into said second i-type layer and having a thickness of W 3  which functions as the cathode of the P-i-n diode.   
     
     
       2. The P-i-n diode of claim 1 wherein W 1   2  /τ is in the range of 20-200 cm 2  /sec where W i  equals W 1  +W 2  -W 3 . 
     
     
       3. The P-i-n diode as claimed in claim 1 wherein the carrier lifetime killer is platinum. 
     
     
       4. The P-i-n diode as claimed in claim 1 wherein the thickness W 1  of the first i-type layer is less than 5 μm. 
     
     
       5. The P-i-n diode as claimed in claim 1 wherein the thickness W 2  of the second i-type layer is approximately 25 μm.